The Visible and Hidden Reservoirs of Purulia

The Visible and Hidden Reservoirs of Purulia

Nov 18, 2023

Raphaela Betz

Tracing the origins of Dwarakeswar River

For the next 5 days, we will be travelling along the Dwarakeswar River with the Development Research Communication and Services Centre (DRCSC). Today, we start at the hilltops of Purulia, which contain the network of small springs and streams that is to become the mighty Dwarakeswar River, who can rise to cause flash floods in the monsoon season. The springs are initially fed by the monsoon as the porous granite rock serves as a concealed natural reservoir in the hills. From these pores, the water is slowly released. The hilly uplands, called “Tnar”, consist of granite rock , which are barely covered in soil. From afar, some of the hills look more like a pile of huge boulders that a giant has played with, while others look like a tortoise back, or small volcanos (although they are not of volcanic origin). The place would be a boulderer’s paradise.

The hills of Purulia, with their distinct shapes and boulder assemblies

The region receives an annual rainfall of around 1000 mm. This is not that little, compared to areas in Western India, which only receive around a third of that. The issue lies in the timing of the rainfall. Most rain falls within a few days, especially now that the monsoon season tends to become more abrupt due to climate change, leading to fewer days of rainfall with higher intensity. Therefore, for perennial water access, the region is dependent on water storage.

In the upcoming days, we will see a kaleidoscope of small and large measures to restore the infiltration of water into the ground and increase storage of water in the region. These measures work together like parts of a well-oiled machine. However, with missing pieces, the functionality can easily be lost.

View from one hill to more hills

Giving and taking water: the region’s trees

One measure to increase water infiltration into the ground that is being promoted by DRCSC is the re-establishment of indigenous vegetation in the region, such as Sal trees, and improving soil health. The surrounding area used to have greater and more diverse trees. Over the decades, some were cut by the British, others were cut by non-tribal people. Now, only scattered trees from the old species remain, and they are complimented by plantages of fast-growing varieties like Eucalyptus. This has led to a critical decline in soil quality, significantly reducing its water absorption capacity.

At the foot of one of the hills, we go with our guide and local hero, Bablu Mandal, through a Eucalyptus plantation in search for some of the small streams. Over the past 30 years, Bablu has made a huge impact on the villages by promoting sustainable farming methods. Everyone here knows him and calls him Bablu Da (Da is Bengali for “older brother”).

While we walk through the neatly planted rows of wood, Bablu explains how the traditional vegetation is actually much better for the soil. The area used to be covered in Sal trees, an indication for rich, healthy soil of several feet depth. Now, mostly Palash and Date trees grow here. These are species that can survive on thin, rocky soil. Monocultures like eucalyptus or acacia are a major cause for soil degradation, explains Bablu. They don’t allow for any other vegetation, so there’s a lack of fresh biomass for soil building. Less soil also means less water storage. It is the soft top layer soil can hold water, while the exposure of the ground’s lower rocky layers can speed up run-off of water after rainfall, ultimately “losing” potential groundwater to the streams.

A young Sal tree, planted by a women’s group in a DRCSC project. They need good soil for growth, so for now they are only growing slowly.

A dried water stream bed in the eucalyptus plantation.

Finding water takes a bit longer. After walking for some time, we come to a crack in the ground where water is tripling slowly out of a rock. Below a tiny pond has formed, from which the water flows very slowly downwards, almost standing. To our disbelief, there are fish in the water. This is one of the many springs that feed the surrounding streams and the Dwarakeswar River.

The natural trees used to increase the water storage capacity in earlier days and their disappearance over the years is part of the reason for the increasing water shortage in the river stream. As the temperature is a mild 27 degrees Celsius today, the vegetation looks green and moist, and the soil is showing no signs of water deprivation, although most of the streambeds are already dry. “If you actually want to know Purulia, you need to come in the early summer”, Bablu says, “that is when it is the driest and hottest, and the water challenges become the most obvious”.

With the limited capacity of water storage within the rocks and the reduced storage capacity of trees, a lot of water is “lost” to the monsoon flows. The intense rain washes through the land in flash floods, leaving barely any time for soil infiltration, which is a process that is much needed to sustain the underground reservoir and nourish the river flow over the year.

Water tripling out of the rock to form a small spring

Reservoirs for improved infiltration, irrigation and drinking water supply

Another strategy being utilised to increase water storage in the region is building surface water reservoirs. We visited one of the smaller reservoirs of the region, Futiyari. The water is held back by an earthen dam. It is designed to overflow if the water level is high. There are no large control gates at the dam. Instead, the dam walls are porous, so the water can slowly drain and trickle into the irrigation channels flowing out from the reservoir. It provides water for 2000 hectares of land. It is one of 32 such reservoirs in the region.

A fisher boat on the Futiyari reservoir

The Futiyari reservoir, with dam wall in the background.

The traditional water provision of the region is dug wells. Boreholes still exist, but the deeper layers of groundwater have high levels of fluoride, which causes disease over long periods of exposure, such as dental fluorosis. Sugata Hazra of DRSCS tells us that the tribal people are less prone to the effects of fluoride due to their diet, as snails and other components in their food can help to release fluoride out of the body.

Now, the reservoirs can provide an alternative source of drinking water for the region and since 2018, a water treatment plant provides drinking water from the Futiyari reservoir to around 100,000 people in the surrounding villages. We are shown around the treatment plant by Manas Sadar, a mechanical engineer, and Palash Banerjee, a supervisor of the reservoir. They explain to us that the reservoir’s water is first filtered and is then chlorinated before it is pumped to the villages. Water samples are regularly brought from the villages to be tested in the treatment plant’s laboratory. Every 15 days, the laboratory controls basic parameters such as pH, turbidity, conductivity, but also faecal bacteria (with E.coli as proxy) and iron. Fluoride and arsenic are tested monthly. The results are sent to the Panchayat, which is responsible for taking action in case of increased levels of any parameters. E.coli is mostly increased during the monsoon season. Before there was a treatment plant, the water used to have a red stain to it, which is a sign for increased iron levels. Now, the treatment plant has improved the appearance of the water.

Water pumps supply treated water to 100,000 surrounding inhabitants.

The reservoirs not only supply drinking water to the region but also provide water storage for agriculture. Therefore, maintaining water supply also requires management of agricultural practises to reduce consumption of water. We talk to a member of the regional irrigation department. The main challenge, he says, is managing the fair distribution of the water. The regional farmers are used to cultivating rice, which is a crop that grows well in the monsoon, when water floods the fields. Small dams, called Aal, around each field make sure that the crops stay wet. Accordingly, cultivation used to be once a year when the monsoon waters are available. Now, with the irrigation scheme, farmers use the water from the reservoirs for a second rice harvest. The problem is that rice is a water-intensive crop and as such, the first 10-30 percent of households along the irrigation channels use up all the water for the cultivation, leaving the rest of the community without water for irrigation of a second harvest. The solution is educating the farmers, he says. They have grown rice all their life and lack knowledge on alternative crops. Better options for the second harvest would be millet, vegetables, or oil seeds like mustard, which need much less water.

Aal, the small earthen bunds around paddy fields, demarcate the fields and keep the water in. For their rice cultivation, farmers redirect the irrigation streams to flood these fields.

Today, we have seen the origins of Dwarakeswar and witnessed the effects of deforestation, mono-culture and changing climatic conditions. A lack of infiltration and storage capacity, such as trees and healthy soil, combined with increasing weather extremes, creates fast run-off in the monsoon streams and causes the deprivation of the local aquifers. We also saw two major strategies to counter-act this: planting traditional tree species that have the capacity to retain water and improve the soil quality, which can further retain more water; and small-scale irrigation reservoirs, which can increase retention time for soil infiltration and directly serve as drinking water sources. In the upcoming days, we will visit several other components of the catchment management scheme, such as ponds, retention walls, trenches and river lift irrigation.